Knee joint for prosthetic appliance

ABSTRACT

An artificial leg with a thigh member and a shank member has an upwardly converging wedge fixedly secured to the shank member in a bearing cylinder rigid with the thigh member with interposition of two freely movable brake segments between the flanks of the wedge and the cylinder wall. When the weight of the user rests on the appliance, the cylinder is lowered so that the wedge spreads the brake segments to rigidify the limb; when the weight is off, a spring raises the cylinder relatively to the wedge which thereupon releases the brake segments from their cylinderengaging position, thus allowing the shank to swing with reference to the thigh.

us: 3,678,517 51 July 25,1972

[54] KNEE JOINT FOR PROSTHETIC APPLIANCE [72] Inventor: Edwin Ehbrecht,3429 Etzenborn 24, Germany [22] Filed: Jan.2l, I971 [2|] Appl.No.:108,480

l,099,570 3/ I955 France ..3/22

Primary Examiner-Richard A. Gaudet Assistant Examiner-Ronald L. FrinksAttorney-Karl F. Ross ABSTRACT An artificial leg with a thigh member anda shank member has an upwardly converging wedge fixedly secured to theshank member in a bearing cylinder rigid with the thigh member withinterposition of two freely movable brake segments between the flanks ofthe wedge and the cylinder wall. When the weight of the user rests onthe appliance, the cylinder is lowered so that the wedge spreads thebrake segments to rigidify the limb; when the weight is off. a springraises the cylinder relatively to the wedge which thereupon releases thebrake segments from their cylinder-engaging position, thus allowing theshank to swing with reference to the thigh.

9 Clfllns, 2 Drlwlng Figures PATENTED M25872 3 57 517 FIG. I

Edwin Ehbrechf Inventor.

KNEE JOINT FOR PROSTHE'I'IC APPLIANCE My present invention relates to aprosthetic limb, more specifically to an artificial leg wherein an upperthigh member and a lower shank member are swingably interconnected by akneejoint.

In such limbs it is desirable to lock the knee joint against relativerotation of the members when the user stands upright, placing his weighton the prosthetic appliance, yet to allow the lower member or shank toswing freely within certain limits when the weight is off, e.g. when theuser is seated.

The general object of my invention is to provide simple and effectivemeans for locking and unlocking the knee joint in response to bodyweight.

This object is realized, pursuant to my present invention, by theprovision of a wedge element received in a cylindrical bore which isformed at the knee joint in one of the two leg mem bers, eg the thigh,the wedge element being rigid with the other member (e.g. the shank) andco-operating with clamping means such as a pair of brake segments whichare loosely inserted in the bore adjacent the wedge flanks for cammingdisplacement thereby into engagement with the wall surface of the boreupon a relative vertical motion of the members due to a loading of thethigh by the weight of the user; for this purpose, the flanks of thewedge element converge in a vertical direction, specifically in thedirection of weight-induced relative motion of the two members (i.e.upwardly if the wedge is carried on the shank). When the appliance isunloaded, the return shift ofthe members within their limited range ofvertical mobility is advantageously assisted by a spring or equivalentbiasing means acting upon the wedge element.

The above and other features of my invention will be described in detailhereinafter with reference to the accompanying drawing in which:

FIG. I is a side-elevational view of part of a prosthetic applianceincluding my improved knee joint; and

FIG. 2 is a cross-sectional view taken on the line ll ll of FIG. 1.

The prosthetic limb shown in the drawing comprises a thigh number I anda shank member 2 interconnected at a knee joint with limited verticalmobility, the shank 2 forming a cradle ll for a generally cylindricalhead 12 of the thigh I. This head has a bore l3 centered on a horizontalaxis 0, the bore being provided with a fixed tubular liner 6 (e.g. ofmetal) advantageously carrying an inner friction layer 7 of the typeconventionally used in brake linings. Within the bore I3 I dispose anupright wedge element 4 which is secured to an extension of shank 2 by apair of parallel horizontal pins 3', 3" and whose flanks 4a. 4b lie onopposite sides of a vertical plane P including the axis 0. These flanksconverge upwardly and are in contact with a pair of brake segments 5a,56 whose edges remote from the wedge 4 are cylindrically curved withsubstantially the same radius as the inner wall surface of the bore,more specifically of brake lining 7; the broad lower face of wedge 4also has the same curvature, as has the narrow upper tip thereof.Between this tip and the bore wall there is inserted a compressionspring 8 tending to raise the tube 6 and thereby the thigh l withreference to the wedge and the shank 2.

In the unloaded position of the appliance, the lower face of wedge 4 isin light frictional contact with layer 7 and the brake segments 50, 5bare loosely held between this wedge and the liner 6, 7; the shank 2 maythen swing freely with reference to thigh l, within limits defined bystops not shown.

When the user rests his weight on the appliance. shank l is depressedagainst the force of spring 8 so that wedge 4 rises within its bore,thereby spreading the brake segment 50, Sb apart into locking engagementwith friction layer 7.

Naturally. members I and/or 2 may be provided with cover plates or thelike, not shown. holding the assembly 5a. 5b in position.

It will thus be seen that l have provided a compact construction for aknee joint exerting an effective clamping force upon its two relativelyswingable members in response to a vertical loading pressure.

Naturally, the prosthetic llmb here disclosed could also be used, withminor modifications, as an arm having two members interconnected by anelbow joint. so long as means (e.g. cables) are provided for relativelystressing these members toward each other.

lclaim:

l. A prosthetic limb comprising a thigh member and a shank memberinterconnected by a knee joint with limited freedom of relative verticalmotion, one of said members being formed at said knee joint with acylindrical bore centered on a horizontal axis; a wedge element in saidbore rigid with the other of said members, said wedge element havinglateral flanks on opposite sides of a vertical plane through said axis,said flanks converging in the direction of relative motion of said otherof said members upon a loading of said thigh member by the weight of auser; and clamping means loosely inserted in said bore adjacent saidflanks for displacement thereby into engagement with the wall surface ofsaid bore upon such weight-induced relative motion.

2. A prosthetic limb as defined in claim I wherein said other of saidmembers is provided with a pair of parallel horizontal pins supportingsaid wedge element thereon.

3. A prosthetic limb as defined in claim I wherein said clamping meanscomprises a pair of brake segments with outer edges conforming to thecurvature of said bore.

4. A prosthetic limb as defined in claim 3 wherein said bore is providedwith a tubular liner surrounding said wedge element.

5. A prosthetic limb as defined in claim 4 wherein said liner includes afriction layer facing said brake segments.

6. A prosthetic limb as defined in claim I. further comprising resilientbiasing means urging said wedge element into a disengaged positionagainst the direction of said weight-induced relative motion.

7. A prosthetic limb as defined in claim 6 wherein said biasing meanscomprises a compression spring inserted between the tip of said wedgeelement and the wall surface of said bore.

8. A prosthetic limb as defined in claim I wherein said wedge element hma broad end face cylindrically curved with substantially the radius ofsaid bore.

9. A prosthetic limb comprising a first member and a second memberinterconnected by a joint with limited freedom of relative verticalmotion, one of said members being formed at said joint with acylindrical bore centered on a horizontal axis; a wedge element in saidbore rigid with the other of said members, said wedge element havinglateral flanks on opposite sides of a vertical plane through said axis,said flanks converging in the direction of relative motion of said otherof said members upon a relative stressing of said members toward eachother; and clamping means loosely inserted in said bore adjacent saidflanks for displacement thereby into engagement with the wall surface ofsaid bore upon such stress-induced relative motion.

0 I O Q

1. A prosthetic limb comprising a thigh member and a shank memberinterconnected by a knee joint with limited freedom of relative verticalmotion, one of said members being formed at said knee joint with acylindrical bore centered on a horizontal axis; a wedge element in saidbore rigid with the other of said members, said wedge element havinglateral flanks on opposite sides of a vertical plane through said axis,said flanks converging in the direction of relative motion of said otherof said members upon a loading of said thigh member by the weight of auser; and clamping means loosely inserted in said bore adjacent saidflanks for displacement thereby into engagement with the wall surface ofsaid bore upon such weight-induced relative motion.
 2. A prosthetic limbas defined in claim 1 wherein said other of said members is providedwith a pair of parallel horizontal pins supporting said wedge elementthereon.
 3. A prosthetic limb as defined in claim 1 wherein saidclamping means comprises a pair of brake segments with outer edgesconforming to the curvature of said bore.
 4. A prosthetic limb asdefined in claim 3 wherein said bore is provided with a tubular linersurrounding said wedge element.
 5. A prosthetic limb as defined in claim4 wherein said liner includes a friction layer facing said brakesegments.
 6. A prosthetic limb as defined in claim 1, further comprisingresilient biasing means urging said wedge element into a disengagedposition against the direction of said weight-induced relative motion.7. A prosthetic limb as defined in claim 6 wherein said biasing meanscomprises a compression spring inserted between the tip of said wedgeelement and the wall surface of said bore.
 8. A prosthetic limb asdefined in claim 1 wherein said wedge element has a broad end facecylindrically curved with substantially the radius of said bore.
 9. Aprosthetic limb comprising a first member and a second memberinterconnected by a joint with limited freedom of relative verticalmotion, one of said members being formed at said joint with acylindrical bore centered on a horizontal axis; a wedge element in saidbore rigid with the other of said members, said wedge element havinglateral flanks on opposite sides of a vertical plane through said axis,said flanks converging in the direction of relative motion of said otherof said members upon a relative stressing of said members toward eachother; and clamping means loosely inserted in said bore adjacent saidflanks for displacement thereby into engagement with the wall surface ofsaid bore upon such stress-induced relative motion.